Telltale spark-plug



I. HARRIS. TELLTALE SPARK PLUG.

APPHCMIUN FILED MAY 21. 19:9.

' 1 343 2 Patented June 15,1920.

I V a awwentoz UNITED. sures PATENT OFFICE.

ISAAC HARRIS, F DETROIT, MICHIGAN.

.TELLTALE SPARK-PLUG.

Application filed May 21-, 1919. .Serial No. 298,659.

- of. Michigan, have invented new and useful Improvements in TelltaleSpark-Plugs, of which the following is a specification.

The obi'ect of the invention is to provide a spark p ug of simple andefficient construction wherein the proper functioning of the terminalsof electrodes is apparent upon inspection without removing the plug orapplying any of those tests which are now in common use in thisconnection, and wherein the tension due to a spark gap inthe sparkingcircuit may be modified at the will of the operator to suit theconditions under which the plug is being employed.

With these and related. objects in view the invention consists in aconstruction, combination and relation of parts hereinafter fullyexplained, it being understood that changes in form, proportion anddetails may be resorted to, within the scope of the claim withoutdeparting from the principles-involved.

Figure 1 is a side view of a spark plug embodying the invention.

Fig. 2 is a longitudinal sectional view of the same.

,Fig. 3 is a transverse sectional view on the plane indicated by theline 3-3 of ig. 4 is a sectional view on the plane indicat'ed on theline 4.-4 of Fig. 2.

The porcelain body portion of the plug is seated within the bowl nut 11upon a suitable gasket 12 where it is held by means of a gland 13threaded into the bowl nut and bearing upon a shoulder 14. Said bowl nutis of polygonal contour to form a wrench seat whereby the threadedsleeve portion 15 thereof may be engaged with the motorhead indicated at16.

The terminals or'electrodes 17 and 18 are arranged in the ordinaryway-comment jump spark plugs "with the latter wh 1c is insulated by theporcelainbody portion and extendsaxially therethrough rovided with acollar 19 which is s aced mm the end wall of the cavity 20 y means of awasher 21 which serves to prevent the passage of gases from.the interiorof the motor cylinder to the bore of the porcelain body. Below thecollar 19 the electrode 18 is preferably provided. with a polygonalwrench seat 22.

This electrode 18 is divided to form elements 23 and 24 which areseparated at their adjacent extremities to form a spark gap locatedwithin a transverse recess 25 in the porcelain body of the plug,metallic reinforcing elements 26 being embedded in the latter adjacentto the recess and the upper portion of said body inclosing the recessedzone thereof being surrounded by a glass or similar transparentprotective shield 27 through the wall of which the interior of therecess 25 and the spark gap may be viewed from the side of the plugwithout removal of the latter from the motor.

The upper extremity of the lower electrode member 23 is threaded andfitted with a nut 28 and the 'lower extremity of the upper member ofsaid electrode is correspondingly fitted with a nut 29 by the adjustmentof which the extent of the spark -gap may be modified while the terminal30 of the electrical connection 31 is engaged by a thumb nut 32 threadedupon the upper end of the upper electrode member and is thereby held incontact with a cap plate 33 which.

bears upon the upper end of the porcelain body of the plug.

Obviously, when the spark plug is roperly. functioning there is at eachstro e of the motor mechanism a spark or flash at the spark gaprepresented by the adjacent extremities of the members of the positiveelectrode 18, and the absence of such a spark is an indication totheoperator that the connections are at fault and and the extent of thegap mines the increase in tension of the current at the sparkingterminals within the en 'ne cylinder andbe varied by the. adgustvious'ly deter.

ing means above described to secure the desired results and theeonditionses they may he found to exist in practice.

Claim A spark plug having an insulating body provided at an intermediatepoint with a transverse terminally open recess, reinforcing elementsembedded in the body adjacent to said recess, a transparent sleeve em-Drawing the body in tlie zone of and closing 10 the extremities of saidrevess and' a sectional electrode having: its members terminallyseparated to. form a spark gap Within said recess.

In testimony whereof I ufiix m \'si;1nnture. 15

ture.

Is'AAo HARRIS.

